CLAUDE.md — IO Module Blazor Dashboard

Project Overview

Blazor Server app (.NET 10) for monitoring and controlling the STM32H723ZG Nucleo IO module. Communicates over CAN (via PCAN-USB adapter) and serial (via ST-Link VCP).

Architecture

PCAN Hardware ──► CanWorker (IHostedService) ──► CanService (singleton) ──► Razor pages
ST-Link VCP   ──► SerialPortService (singleton, event-driven)           ──► SerialTerminal.razor

Blazor Server — all C# runs server-side; browser connects via WebSocket/SignalR
No background worker for serial — System.IO.Ports.SerialPort fires DataReceived events internally; SerialPortService handles buffering directly

Key Files

File	Purpose
`Services/ICanService.cs` / `CanService.cs`	PCAN adapter: send, receive, filter, signal extraction
`Services/ISerialPortService.cs` / `SerialPortService.cs`	Serial port: open/close, send lines, receive buffer
`CanWorker.cs`	`IHostedService` — continuous CAN RX loop, loads config from `appsettings.json`
`Models/CanModels.cs`	`CanMessageDto`, `CanFilter`, `CanBitmask`
`Components/Pages/Home.razor`	Button status + termination toggles + CAN message list
`Components/Pages/CanMonitor.razor`	Full CAN UI: connect, stream, filters, bitmasks, send
`Components/Pages/SerialTerminal.razor`	Serial terminal for NVMEM commands

CAN Sending Pattern

// PcanMessage.Data is read-only — pass data via the constructor, NOT object initializer + CopyTo
var data = new byte[8];
data[0] = payload;
var msg = new PcanMessage(0x240, MessageType.Standard, 8, data, false);
var result = CanService.Write(msg);  // returns PcanStatus.OK on success

UI State Update Pattern

Pages poll CanService.GetLatestMessages() via a Timer (50ms on Home, 100ms on CanMonitor):

_updateTimer = new Timer(_ => InvokeAsync(() => { /* update state */ StateHasChanged(); }), null, 0, 50);

Serial terminal subscribes to ISerialPortService.DataReceived event instead of polling.

CAN Message Map

ID	Direction	Handler
0x210	RX	User button → `button1Active` in Home.razor
0x220	RX	CN9-29 button → `button2Active`
0x230	RX	CN9-30 button → `button3Active`
0x240	TX	Termination control — sent from `Home.razor:SendTermination()`
0x250	RX	Termination pin status — bit0=TERM_ON, bit1=TERM_OFF; syncs `_termOn`/`_termOff` in Home.razor
0x241	TX	NVMEM write — sent from SerialTerminal via CAN (if needed)
0x242	TX	NVMEM read request
0x243	RX	NVMEM read response

CAN Config (`appsettings.json`)

"CanOptions": {
  "Channel": "",          // empty = auto-scan PCAN USB
  "Bitrate": "Pcan500",
  "Filters": [],          // CanFilter objects
  "Bitmasks": []          // CanBitmask objects for signal extraction
}

Serial Port Notes

SerialPortService is a singleton — only one port open at a time
Buffers last 200 lines; sent lines prefixed > , received prefixed <
NVMEM commands: r <addr_hex> <len> and w <addr_hex> <bytes...> at 115200 baud
Full command reference: ../STM32Nucleo/docs/NVMEMCommands.md

Build / Run

dotnet run --project IOModuleTestBlazor

Requires PCAN-Basic drivers installed. Serial port access requires the app to run with permission to open COM ports (no special config needed on Windows).

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